This patch makes a very small change to the function that determines if a
timestamp is close to the current day, which is used for showing/hiding items in
agenda views.

Under current behavior, a deadline of today is close only if it has some amount
of lead time. If your date is 2016-06-01, the following statements evaluate to
nil:
#+BEGIN_SRC emacs-lisp
(org-deadline-close "2016-06-01 Wed -0d") ;; but this is today!
(org-deadline-close "2016-06-02 Wed -1d")
#+END_SRC

One effect of this is that if you set =org-agenda-todo-ignore-deadlines= to
=far= and generate the TODO list agenda view (C-c a t), then items only appear
if you are one day past the point at which they should appear. For example, the
following item does not show up in my current TODO list:
#+BEGIN_EXAMPLE
* TODO due today, no lead time
DEADLINE: <2016-06-01 -0d>
#+END_EXAMPLE